COSMO Limited-Area Ensemble Prediction System

Last updated: March 2018

COSMO-LEPS is the Limited Area Ensemble Prediciton System developed within COSMO consortium
in order to improve the short-to-medium range forecast of extreme and localised weather events.
It is made up of 20 integrations of COSMO model, which is nested on selected members of ECMWF ENS.

1. Basic model set-up

COSMO-LEPS started to run on an experimental-operatonal basis on November 2002 and, in November
2005, it became an ECMWF member-state time-critical application, managed remotely by Arpae-SIMC.

COSMO-LEPS runs twice a day, starting at 00 and 12UTC, using a 7 km grid spacing and 40 vertical
layers, with a forecast range of 132 hours. The computer time to run the system at ECMWF is provided
by a joint account, with the contributions of the COSMO countries which are also ECMWF member state
(namely, Greece, Germany, Italy and Switzerland).

The rotated lat-lon coordinates of the lower left and upper right corner of the integration domain
are lon=-15.75, lat=-16.125 and lon=16.125, lat=9.75, respectively. The coordinates of the Southern
pole of rotation are: latitude=-40N, longitude=10E.

The orography (height in m) of the COSMO-LEPS integration domain.

2. Changes

1 December 2016

COSMO-LEPS increases the ensemble size from 16 to 20 members run in Single Precision; no SPPT by
now for stability problems.

24 October 2016

COSMO-EU fields are no more used: ICON-EU data are used instead.

1 April 2015

No more use of IFS-Bechtold convection scheme; all members use Tiedtke scheme.

18 February 2014

No more use of Kain-Fritsch scheme (which is no more maintained); members 1-8 use Tiedtke
convection scheme, members 9-16 use IFS-Bechtold convection scheme.

6 February 2006

1 July 2005

the forecast length is increased from 120 to 132 hours

COSMO-LEPS products are archived on MARS

6 June 2005

COSMO-LEPS products are archived every 3 hours

25 September 2004

the LM-det run is also produced; it is a further run of COSMO nested on the high-resolution
deterministic forecast of ECMWF in the same configuration as COSMO-LEPS integrations (10 km,
32 ml, 120h range).

3. Operational schedule

As for the 00UTC (12UTC) run, COSMO-LEPS application starts at about 07.30UTC (19.30UTC), once the
ECMWF ENS has passed fc+144h forecast range. Products are disseminated to Met Ops rooms of COSMO
weather offices starting from about 08.30UTC (20.30UTC).